Anisotropic bacterial cellulose hydrogels with tunable high mechanical performances, non-swelling and bionic...

Water-rich hydrogels with tissue-like softness, especially ion conductive hydrogels with ion signal transfer systems similar to biological areas, are promising soft electrode materials, while too poor or unstable mechanical properties that come from uncontrollable swelling and biocompatibility issues caused by introducing high concentration ions are serious obstacles in practical applications. Herein, a simple method for fabricating strong, stable, ion-conductive, anisotropic bacterial cellulose hydrogels (ABCHs) is first reported. Relying on nanofibers with high aspect ratio in bacterial cellulose (BC), a tailor-made nanofiber-network-reinforced structure is constructed by controlled dissolution, followed by aligning them well via a simple fossilizing process under stretching. Therefore, tunable high mechanical performances can be achieved and the maximum tensile strength can reach 14.3 MPa with 70% water content. It is worth noting that ABCHs will not swell in water for 30 days and maintain 93% tensile strength. Most importantly, the unique nanofluid behaviors from nanochannels in nanofibers allow effective ion transport in ABCHs relying only on low concentrations of ions in body fluids (<300 mM), avoiding sacrificing biocompatibility to achieve useful conductivity. This facile strategy might be very scalable in fabricating high-strength, non-swelling, bio-ion conductive cellulose hydrogels for application in next-generation bio-interfacing and flexible implantable devices.